/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jdbc.support.incrementer;

import org.springframework.dao.DataAccessException;
import org.springframework.dao.DataAccessResourceFailureException;
import org.springframework.jdbc.datasource.DataSourceUtils;
import org.springframework.jdbc.support.JdbcUtils;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * Abstract base class for {@link DataFieldMaxValueIncrementer} implementations that use
 * a database sequence. Subclasses need to provide the database-specific SQL to use.
 *
 * @author Juergen Hoeller
 * @see #getSequenceQuery
 * @since 26.02.2004
 */
public abstract class AbstractSequenceMaxValueIncrementer extends AbstractDataFieldMaxValueIncrementer {

    /**
     * Default constructor for bean property style usage.
     *
     * @see #setDataSource
     * @see #setIncrementerName
     */
    public AbstractSequenceMaxValueIncrementer() {
    }

    /**
     * Convenience constructor.
     *
     * @param dataSource      the DataSource to use
     * @param incrementerName the name of the sequence/table to use
     */
    public AbstractSequenceMaxValueIncrementer(DataSource dataSource, String incrementerName) {
        super(dataSource, incrementerName);
    }


    /**
     * Executes the SQL as specified by {@link #getSequenceQuery()}.
     */
    @Override
    protected long getNextKey() throws DataAccessException {
        Connection con = DataSourceUtils.getConnection(getDataSource());
        Statement stmt = null;
        ResultSet rs = null;
        try {
            stmt = con.createStatement();
            DataSourceUtils.applyTransactionTimeout(stmt, getDataSource());
            rs = stmt.executeQuery(getSequenceQuery());
            if (rs.next()) {
                return rs.getLong(1);
            }
            else {
                throw new DataAccessResourceFailureException("Sequence query did not return a result");
            }
        }
        catch (SQLException ex) {
            throw new DataAccessResourceFailureException("Could not obtain sequence value", ex);
        }
        finally {
            JdbcUtils.closeResultSet(rs);
            JdbcUtils.closeStatement(stmt);
            DataSourceUtils.releaseConnection(con, getDataSource());
        }
    }

    /**
     * Return the database-specific query to use for retrieving a sequence value.
     * <p>The provided SQL is supposed to result in a single row with a single
     * column that allows for extracting a {@code long} value.
     */
    protected abstract String getSequenceQuery();

}
